Cooling sleeve for shaft and bearing for high temperature gas moving system

ABSTRACT

A cooling sleeve for the drive shaft of a draft inducer fan within a plenum extends into the plenum from a plenum wall. The fan drive shaft passes through the cooling sleeve and is fixed to a bearing spaced from and attached to the plenum wall on the outside of the plenum. By means of this construction, the bearing can be maintained at a safe cool operating temperature relative to the temperature of gases within the plenum.

United States Patent [191 Nozaki 1 COOLING SLEEVE FOR SHAFT AND BEARING FOR HIGH TEMPERATURE GAS MOVING SYSTEM [75] Inventor: Michio B. Nozaki, LaGrange, 111.

[73] Assignee: Rheem International, Inc., New York, NY

[22] Filed: Mar. 18, 1971 [21] Appl. N0.: 125,518

[52] US. Cl 126/112, 308/77, 415/180,

287/189.36 F [51] Int. Cl. F24h 3/00 [58] Field of Search 308/76, 77, 189 R, 15;

[56] References Cited UNITED STATES PATENTS 2,961,760 11/1960 Horton et a1. 287/189.36 F

oooooooooooooooolooo ooo Apr. 16, 1974 3,403,962 10/1968 Suffron et a1. 431/20 616,590 12/1898 Seymour, Jr 308/77 2,665,059 1/1954 Newton 4 308/77 2,755,989 7/1956 Coward 415/180 X Primary Examiner-William E. Wayner Attorney, Agent, or Firm-Mo1inare, Allegretti, Newitt & Witcoff 5 7] ABSTRACT A cooling sleeve for the drive shaft of a draft inducer fan within a plenum extends into the plenum from a plenum wall. The fan drive shaft passes through the cooling sleeve and is fixed to a bearing spaced from and attached to the plenum wall on the outside of the plenum. By means of this construction, the bearing can be maintained at a safe cool operating temperature relative to the temperature of gases within the plenum.

1 Claim, 4 Drawing Figures PATENTEDAPR 16 I914 v 3804.073

SHEET 1 OF 2 /4- ooawooooooaoaoolwmfima IN VENTOR.

-l M/CH/O B. NOZA/(l PATENTEUAPR 16 1974 SHEET 2 [IF 2 R Z Y E v MAJAT COOLING SLEEVE FOR SHAFT AND BEARING FOR HIGH TEMPERATURE GAS MOVING SYSTEM BACKGROUND OF THE INVENTION This invention relates to a cooling sleeve construction for a member, such as a fanshaft, which projects through a plenum wall. The apparatus is especially useful to prevent overheating of bearings or instruments external a plenum, despite the high temperature that may exist within the plenum.

It is often desirable to induce a draft above the combustion chamber in a heating system. This is desirable in order to draw the heated gases from the combustion chamber for use in other locations such as for the heating of water. One of the means for drawing or inducing a draftabove a combustion chamber is by use of a fan in a plenum positioned over the combustion chamber. Such a fan will typically be driven by an electric motor which is external to the plenum and which drives a fan shaft extending through the plenum wall.

Also, in order to measure, for example, the draft induced by such a fan, some type of sensor may be positioned within the plenum. A shaft member may then extend from that sensor through the plenum wall to a control device mounted external the plenum chamber.

It has been found that the temperature of the heated air and exhaust gas within the interior of the plenum may approach 600 F. Of course, the fan, the fan shaft, and various other components within the plenum will be heated to these and even higher temperatures due to the radiation within the combustion chamber. Likewise, the walls of the plenum will become heated to temperatures of 250 to 350 F.

It is at this juncture that problems often arise since bearings for the fan shaft, for example, which are normally fixed to the plenum walls must be specially constructed and specially lubricated if they are to be operated at temperatures above 250 F. Likewise, control devices which are operated by sensors positioned within the plenum cannot normally toleratesuch high temperatures unless they are specially designed and manufactured. In an effort to overcome the necessity of special bearings and special controls designed for high temperature applications, the present invention has been made.

SUMMARY OF THE INVENTION In a principal aspect, the present invention comprises a cooling sleeve and housing for a member which projects through a plenum wall, wherein a temperature gradient exists across the plenum wall. The sleeve is comprised of hollow tubular means which project from the plenum wall toward the direction of increasing temperature. The member extends in both directions be-' I of the plenum 18.

It is a further object of the present invention to provide means for mounting bearings or controls external a plenum wherein the bearings or controls are protected from high temperatures even though temperatures of the plenum and on the interior of the plenum would be high enough to cause failure of the bearings or the controls.

One further object of the present invention is to provide an economical and easily incorporated cooling arrangement for apparatus extending into a plenum of a draft induced heating apparatus. v I

These and other objects, advantages and features of the present invention will be set forth in greater detail in the description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS In the detailed description which follows, reference will be made to the drawings comprised of the following FIGURES:

FIG. 1 is a crosssectional view of a combustion chamber with a draft inducer plenum thatincludes the cooling sleeve of the present invention;

FIG. 2 is an enlarged cross-sectional view of the cooling sleeve as indicated by the numeral 2 in FIG. 1; v

FIG. 3 is a cross-sectional view of the apparatus shown in FIG. 1 taken substantially along the line 33 in FIG. 1 and illustrating an embodiment wherein a sensor positioned within the draft inducer plenum operates a shaft connected to a switch external the plenum; and

FIG. 4 is a cross-sectional view of the switch cooperable with the sensor of FIG. 3 taken substantially along the line 44 in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS ers 14 are positioned in the lower part of. the chamber 10 and are provided, for example, with a gas-:air mixture which is ignited and combusted to produce heat. The hot combustion products pass'upwardly over thin tube heat exchangers l6 and thence into a draft inducer plenum 18.

The plenum 18 is defined by plenum side walls 20 and 22 in FIG. 1, walls 23 and 25 in FIG. 3 and a plenum top 24. A cylindrical exhaust duct or flue pipe 26 extends upwardly from a flue opening 28 in the top 24 Attached to the inside of the plenum 18 beneath the flue opening 28 is a blower scroll 30. A blower wheel 32 mounted for rotation on a shaft 34 is positioned within the scroll 30. The blower wheel 32 operates to exhaust flue products through the flue pipe 26. Typically, the draft inducer blower wheel 32 is driven by a belt around apulley 36 attached to shaft 34.

What has been described so far is typical of apparatus well known in the art and is by no means limiting of the features of the invention. Rather, adescription of the heating apparatus described so far is a typical environment for use of the present invention. The exhaust gases in the plenum 18 typically have a temperature of 575 to 600 F. However, the components within the plenum 18 such as the scroll 30 and wheel 32 assume even higher temperatures because of radiation from the combustion flame at the burners l4 and further radiation that may be reflected by refractory materials 35 in FIG. 3 used inside the combustion chamber 10.

Further, although the plenum 18 is generally directly exposed to room temperature, the wall temperature is on the order of 250 to 350 F. Consequently, the driving components for the blower wheel 32 such as bearings 38 and 39 for the shaft 34 must be protected from corrosion, thermal degradation, and deformation. It has been found that if the blower shaft 34 is supported by ordinary bearings mounted directly on the walls and 22, then the shaft 34 and the bearings and pulley 36 will be overheated. Generally, the service temperature of standard bearings is limited to 250 F. Otherwise, special lubricants and special bearing components must be utilized for higher temperature application.

Referring now to FIG. 2, there is illustrated in detail the improvement of the present invention which is utilized to reduce the temperature of the shaft 34 and its bearings 38 and 39. An opening is provided in the plenum wall 22 and a cylindrical sleeve 40 having an outwardly flared mounting flange 42 is positioned through the opening. A hearing mounting assembly 44 serves to mount the bearing 38 for the shaft 34 as well as to hold the cylindrical sleeve 40 in position. Sleeve 40 extends substantially perpendicular from plenum wall 22 toward the interior of plenum 18. The bearing mounting assembly 44 also provides means for attachment of the bearing 38 a fixed distance from the plenum wall 22 on the lower temperature side of plenum wall 22.

Each bearing mounting assembly 44 is comprised of a bolt 46 which passes through an opening provided in bearing 38. A nut 48 secures the bearing 38 to the bolt 46. A spacer 50 is positioned between nut 48 and flange 42. A second nut 52 fastens the bolt 46 to the plenum wall 22 and holds it in fixed position. While two such bearing mounting assemblies 44 are shown in FIG. 2, the number of assemblies is not to be limited in any way, the number being determined by the structural requirements to adequately support a shaft 34 and bearing 38.

The assemblies 44 hold and support shaft 34 by means of bearing 38a distance w from the wall 22. The distance w, is dependent upon the desired air flow into sleeve 40. That is, as w, increases, more air can flow into sleeve 40. Simultaneously as W increases, less heat will be conducted to the bearing by assemblies 44. The bearing 38 will, therefore, be cooled by the air flow and will not be heated as much by heat transfer from the plenum 18. I

The cylindrical sleeve 40 has a radius .r, which is greater than the radius y 'of the shaft 34 so that air or fluid from the lower temperature side of plenum wall 22 may flow past the bearing 38 and through the sleeve 40 to the interior of the plenum 18 as illustrated in FIG. 1. In this manner, the flow of fluid cools the bearing 38 as well as the attached shaft 34. This provides a cooling effect along the end of the shaft 34 near the bearing 38. Typically, the radius x, of the sleeve 40 will be in the range of 4 to 5 times the radius y, of the shaft 34.

Note that it is particularly important that the sleeve 40 extend for some distance z. into the interior of the plenum 18. However, the sleeve 40 may extend in opposite directions from the plenum wall 22, and the invention is not to be limited to extension only in one direction from the wall 22. Typically, the length 2; of the sleeve 40 is l2 times the radius x, of the sleeve 40.

These typical measurements may vary somewhat with the temperature gradients across the wall 22 and with the fluid that is involved as the cooling medium. Another design feature which is to be considered is the heat characteristics of the materials which comprise the shaft 34 and the sleeve 40.

Utilization of such an arrangement in an embodiment as shown in FIG. 1 and under temperature conditions as described above has resulted in maintenance of the bearings 38 and 39 at temperatures below 190F. Likewise, the shaft 34 and the pulley 36 have been protected from overheating, thereby eliminating thermal degradation of the shaft 34 and pulley belt.

Referring now to FIGS. 3 and 4, there is shown a cross-sectional view of heating equipment shown in FIG. 1 taken at a right angle to the view shown in FIG. 1. Thus, the like components of the apparatus of FIG. 3 include like numbers. Also illustrated in FIG. 3 is a second embodiment of the invention wherein a switch device 60 is positioned external plenum wall 23. The switch 60 cooperates with a shaft or control member 62 which is in contact with a sail 64. This apparatus is commonly known as a sail switch and operates in response to fluid pressure impinging on the sail 64.

Referring now to FIG. 4, there is shown in greater detail the construction of the second embodiment of the invention. Switch 60 is mounted on brackets 66 and 68 which fix the switch 60 a desired distance from the plenum wall 23. A cooling sleeve 70 is also attached to the plenum wall 23. Thesleeve 70 includes an inwardly extending flange 72 which defines an opening 74 through the end of the cooling sleeve 70. The shaft 62 thus projects through the opening 74 and is connected with the sail 64. Air which cools the shaft 62 flows through the opening 74 at a greater rate than it does through the remaining part of the sleeve 70, thereby tending to accentuate the cooling effect in this region near the opening 74. Again, the relationships between the various ra dial distances x and y and the length of the sleeve 70 z are substantially the same as set forth above for the embodiment shown in FIG. 2.

The distance at which the switch 60 is set away from the plenum wall 23 isrepresented by the letter 'w So long as the distance W2 permits free flow of air into the sleeve 70, it does not affect the cooling characteristics of the sleeve 70. Thus, the area for air flow past the brackets 66 and into the open end of the sleeve 70 is normally greater than or equal to the smallest crosssectional area of the sleeve 70. Of course, the distance w may be increased to effectively decrease the radiation transmission of heat to the switch 60, and the brackets 66 and 68 may be constructed to minimize the conduction of heat-to the switch 60. This may be done by controlling the size of the brackets 66 and 68 as well as the materials from which they are made.

What is claimed is:

1. An improved cooling sleeve and bearing mounting construction for a hot air furnace comprising, in combination:

a plenum wall for said furnace;

r 0 outside of said wall;

a plurality of fasteners positioned about the periphery of said bracket and extending through said flange and connected with said wall; and

spacers intermediate said bracket and said flange to rigidly support said flange against said wall and for separating and spacing said bracket from said wall to permit a cooling air flow into said cylindrical housing and said furnace.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No s H 75 I Dated April 16 197A In ento B- It is certified that error appears in the above-identified patent and that saideLetters Patent are hereby corrected as shown below:

On the title page, item [75] should read as follows:

- Rheem Manufacturing Company, a corp. of

Calif. New York, N. Y.

Signed and sealed this 10th dayof December 1974.

(SEAL) Attest 3 MCCOY M. GIBSON" JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents USCOMM'DC 6D376-P69 U.S. GOVERNMENT PRINTING OFFICE 869- 9 0 FORM PO-1OSO (10-69) 

1. An improved cooling sleeve and bearing mounting construction for a hot air furnace comprising, in combination: a plenum wall for said furnace; an opening in said wall through which a rod member projects from outside the furnace to the inside of the furnace; an open ended cylindrical housing including an outwardly extending circumferential flange at one end, said housing extending through said wall opening into said furnace concentrically with said rod and spaced from said rod to form an air flow passage, said flange engaging the outside surface of said wall; a rod support member mounted in a bracket on the outside of said wall; a plurality of fasteners positioned about the periphery of said bracket and extending through said flange and connected with said wall; and spacers intermediate said bracket and said flange to rigidly support said flange against said wall and for separating and spacing said bracket from said wall to permit a cooling air flow into said cylindrical housing and said furnace. 